Synthesis of ¹⁸F-labeled neurotensin(8-13) via copper-mediated 1,3-dipolar [3+2]cycloaddition reaction

The copper(I)-mediated 1,3 dipolar [3+2]cycloaddition between terminal alkynes and azides, also referred to as click-chemistry, was used to synthesize a ¹⁸F-labeled neurotensin(8-13) (NT(8-13)). 4-[¹⁸F]Fluoro-N-(prop-2-ynyl)benzamide [¹⁸F]1 as novel terminal alkyne building block could successfully be coupled with azide-functionalized NT(8-13) 4 to give the corresponding ¹⁸F-labeled NT(8-13) derivative [¹⁸F]5 product in 66% yield as determined by radio-HPLC. The in vitro binding affinity of 18F-labeled NT(8-13) derivative [¹⁸F]5 was determined to be 66 nM.